Besides providing the same configuration as Rails::Engine and Rails::Railtie, the application object has several
specific configurations, for example “cache_classes”,
“consider_all_requests_local”, “filter_parameters”, “logger” and so forth.

In the above example, the configuration from the first application was used
to initialize the second application. You can also use the
initialize_copy on one of the applications to create a copy of
the application which shares the configuration.

If you decide to define rake tasks, runners, or initializers in an
application other than Rails.application, then you must run
those these manually.